Recording film having removable antistatic layer

ABSTRACT

This application describes an image-recording film comprising a film support and a silver halide emulsion layer thereon, characterized in that there is provided in superposition on the emulsion side of the assembly a layer of a film-forming material which is soluble or dispersible in water or alkali and, as the outer layer, a layer of acid-reacting polymer having dispersed therein an acid-reacting carbon black.

Inventors Edward William Lee;

Frank Percy Lambert, both of Ilford, England Appl. No. 26,807 Filed Apr. 8, 1970 Patented Dec. 28, 1971 Assignee Ilford Limited lliord, England Priority Apr. 14, 1969 Great Britain RECORDING FILM HAVING REMOVABLE ANTISTATIC LAYER 4 Claims, No Drawings US. Cl 346/135, 96/83, 96/87 A, 117/201, 117/216, 117/218 Int. Cl ..G01d 15/34 Field of Search 346/135,

References Cited UNITED STATES PATENTS Young Thompson et a1. Salminen et a]. Dubbe et a1. Dubbe et a1.

Primary Examiner-Joseph W. l-lartary Att0rneyCushman, Darby & Cushman 117/34 X 117/34 96/87 A 346/135 X 346/135 RECORDING FllLMl HAVING REMOVABLE ANTISTATEC LAYER This invention relates to image-recording films.

in recent years there has arisen a demand for recording materials which will record an image under the action of an electron beam. Normal photographic films, consisting of a film support carrying a silver halide emulsion, usually a gelatino silver halide emulsion will record an image on exposure to an electron beam and it is possible to produce such 1 products which are particularly sensitive thereto.

A difficulty which arises is that the effect of electrons falling on the emulsion is usually not only to form the desired image but also to charge the emulsion negatively. An emulsion so charged will of course tend to repel electrons moving towards it and it is accordingly necessary to conduct the charge away. Hitherto it has been proposed to do this in the conventional way by providing a backing to the film of a so-called antistatic material. A very wide variety of such antistatic materials have been described for use in the production of photographic materials.

This technique, however, has been found to afford results which are substantially less effective in discharging the film than is required in the particular case where the film is used for electron beam recording.

[t is accordingly an object of the present invention to provide a method and materials for overcoming the disadvantages referred to and ensuring an improved discharge of the film.

According to the present invention there is provided an image-recording film comprising a film support and a silver halide emulsion layer thereon, characterized in that there is provided in superposition on the emulsion side of the assembly a water-or alkali-soluble or-dispersible layer and, as the outer layer, a layer of acid-reacting polymer having dispersed therein an acid-reacting carbon black.

It will be noted that such a product would be quite useless for normal photographic purposes since the carbon black would act as a barrier to light falling on the film. However such a layer is permeable to a beam of electrons and its opacity to light is therefore, for the purpose for which the film is intended, irrelevant. The carbon black layer acts as an antistatic layer and should preferably have a resistivity not greater than ohms/square.

A suitable first, or supercoat, layer is one applied from an aqueous solution of a water-soluble polymer. Suitable materials for the purpose are the water-soluble cellulose ethers, e.g. cellulose hydroxyethyl ether (for instance as sold under the Registered Trademark NATROSOL) or cellulose hydroxypropyl ether (for instance as sold under the Registered Trademark KLUCEL) or other water-soluble cellulose derivatives such as the sodium salt of carboxymethyl cellulose, or water-soluble vinyl polymers such as polyvinyl alcohol and polyvinyl alcohol ethers such as the hydroxy ethyl ether of polyvinyl alcohol, or water-soluble carbohydrate materials such as the synthetic sucrose product sold under the Registered Trademark FICOLL.

Only a thin supercoat is in any event necessary-e.g. a coating of about 5 mg. per square decimeter.

If desired the supercoating composition may contain a wetting agent of conventional type.

The carbon black coating is preferably one made by the use of an acid-reacting channel black; a very suitable carbon black is that sold under the name DEGUSSA 1,000 V. The medium in which the carbon black is dispersed may be any acidic polymer medium known per se from the literature for the dispersion of carbon black in the production of a carbon-black antistatic layer.

The polymer medium for the carbon black is preferably a polymer mixture of which the elements have been selected to afford a final polymer layer of good mechanical properties, in which the carbon black is well dispersed and which is inert to the photographic emulsion.

It is found, in general, that excellent dispersion of the acidreacting carbon black can be effected in a polymer containing nitro groups, more particularly a copolymer of nitrostyrene or a nitro vinyl toluene with acrylic acid, or other ethylenically unsaturated acid-reacting monomer copolymerizable therewith. However as nitrated polymers may have some effect on the photographic emulsion it is preferred to dilute such a polymer with an inert polymer, so that, for example, the proportion of nitrated polymer in the total polymer is not more than 30 percent by weight, preferably 10 to 30 percent by weight.

The diluent polymer may be any inert polymer but it has been found desirably to include in it a copolymer of methyl methacrylate and methacrylic acid (or other acrylic polymer containing free acid groups) and a proportion of a relatively hard polymer to provide adequate abrasion resistance to the final coating. A suitable relatively hard polymer is, for example, the condensation product of p-hydroxybenzoic acid and dimethylol cresol.

A suitable organic solvent medium may be employed including for example, methyl ethyl ketone, methanol, methyl cellosolve or toluene or mixtures of these,

The image-recording film of the present invention, after imagewise exposure to radiation which can penetrate the carbon black layer and form a latent image in the silver halide, may be processed conventionally or by specific procedure designed to afford particular image characteristics of density and contrast. The carbon black layer may be removed by an initial treatment with water or dilute alkali which will dissolve the interlayer and thus remove both the interlayer and the carbon black layer. Alternatively these layers will be removed automatically during the normal alkaline development procedure.

While, as noted above, the film of this invention may be exposed by an actinic radiation which will penetrate the carbon black coating it is of the greatest importance in connection with electron beam recording. According, therefore, to another aspect of the present invention there is provided a process for the production of an image record which comprises exposing to electron beam radiation an image-recording film as hereinbefore defined, processing the silver halide emulsion of said film to form a visible image and removing the carbon black layer therefrom.

The following examples will serve to illustrate the invention:

ln these examples, the nitrostyrene/acrylic acid resin has a acid value of about 300 mg., KOH/gm. methylmethacrylate and methacrylic acid copolymer has an acid value of about 150 mg. KOH/gm. and the p-hydroxy benzoic acid condensate contains two mol of acid and 1 mol cresol and has an acid value of about 300 mg. KOH/gm.

EXAMPLE 1 A recording film is prepared comprising a film base bearing a gelatino silver halide emulsion designed for electron beam recording. The emulsion layer is coated with two successive layers as follows:

First Layer Coating composition:

Cellulose hydroxyethyl ether l.0 g, Water (distilled) ml. Ethanol 20 ml Wetting Agent (the material sold under the name TEEPOL and having 30 percent active constituent) 0.05 ml.

(The ethanol is included to increase the drying rate of the layer but where this is not important it can be replaced by an equivalent amount of distilled water).

Second layer Coating composition: Carbon black (Degussa L000 v.) l.37% Copolymer of nitrostyrene and acrylic acid 0.84% Copolymer of methyl methacrylate and methacrylic acid l.88% Condensation product of p-hydroxybenzoic acid and dimethylol cresol 0.47% Methanol 44.2% Methyl ethyl ketone 43.0% Methyl cellosolvc 7.3% Toluene 0.4%

EXAMPLE II A recording film is prepared comprising a film base bearing a gelatino silver halide designed for electron beam recording. The emulsion layer is coated with two successive layers as follows:

First layer Coating composition:

without detriment to the washoff characteristics.

EXAMPLE III A recording film is prepared comprising a film base bearing a gelatino silver halide emulsion designed for electron beam recording. The emulsion layer is coated with two successive layers as follows:

First layer Coating com position: Sodium salt of carboxymcthyl cellulose 02 g.

Methanol ml. Water (Distilled) 10 ml.

Second layer Coating composition: Carbon black (Degussa L000 v.) 0.7 g. Copolymer ol' nitrostyrene and acrylic acid 0.7l g. Copolymer of methacrylate and acrylic acid L6 g Condensation products of p-hydroxybenzoic acid and dimethylolcrcsol 0.4 3. Methyl ethyl kctone 45.2 ml. Methyl cellosolve 6.4 ml. Toluene 0.4 ml.

This gives an improvement in scratch resistance in the absence of a wax coating.

A film provided with coating as aforesaid is found to be of greatly improved value for electron beam recording since the difficulties arising from the charging of the emulsion layer are wholly or very largely eliminated.

The recording films of the present invention may if desired also have a second antistatic layer on the back (i.e. the film side) of the film. This can be of any conventional type but is conveniently of the same type as the carbon black layer used for the emulsion side of the film. In that event it is preferably itself supercoated with a polymer layer, e.g. any of the polymers referred to above. Advantageously that supercoated polymer layer may carry a very thin wax coating to lubricate the film.

The present invention includes not only the new recording films herein set forth but also the methods for their production and the methods of electron beam recording using the same.

We claim:

1. An image-recording film comprising a film support and a silver halide emulsion layer thereon, characterized in that there is provided in superposition on the emulsion side of the assembly a layer of an alkali metal salt of carboxy methyl cellulose and, as the outer layer, a layer of acid-reacting polymer having dispersed therein an acid-reacting carbon black, the acid reacting polymer being a polymer mixture containing 10 to 30 percent by weight of a copolymer of a monomer selected from the class consisting of nitrostyrene and nitro vinyl toluene, with an ethylenically unsaturated monomer copolymerizable therewith.

2. An image-recording film according to claim 1 wherein the acid reacting polymer comprises 10 to 30 percent by weight of a copolymer of nitrostyrene and acrylic acid.

3. An image-recording film according to claim 1 wherein the polymer mixture includes a copolymer of methyl methacrylate and methacrylic acid.

4. An image-recording film according to claim 1 wherein the polymer mixture includes a condensation product of phydroxybenzoic acid and dimethylol cresol. 

2. An image-recording film according to claim 1 wherein the acid reacting polymer comprises 10 to 30 percent by weight of a copolymer of nitrostyrene and acrylic acid.
 3. An image-recording film according to claim 1 wherein the polymer mixture includes a copolymer of methyl methacrylate and methacrylic acid.
 4. An image-recording film according to claim 1 wherein the polymer mixture includes a condensation product of p-hydroxybenzoic acid and dimethylol cresol. 